Hi Florian,
If a respin is necessary for this 2/2 too, consider two nitpicks below.
On 15-08-25 11:47:18, Randy Dunlap wrote:
> On 08/25/15 10:40, Florian Fainelli wrote:
> > Add a document describing the Broadcom Starfigther 2 switch hardware,
> > its specifics, and how the driver is implemented and its specifics.
Redundant "specifics" word.
> >
> > Signed-off-by: Florian Fainelli <f.faine...@gmail.com>
> > ---
> > Documentation/networking/dsa/bcm_sf2.txt | 113
> > +++++++++++++++++++++++++++++++
> > 1 file changed, 113 insertions(+)
> > create mode 100644 Documentation/networking/dsa/bcm_sf2.txt
> >
> > diff --git a/Documentation/networking/dsa/bcm_sf2.txt
> > b/Documentation/networking/dsa/bcm_sf2.txt
> > new file mode 100644
> > index 000000000000..7b1502bb707d
> > --- /dev/null
> > +++ b/Documentation/networking/dsa/bcm_sf2.txt
> > @@ -0,0 +1,113 @@
> > +Broadcom Starfighter 2 Ethernet switch driver
> > +=============================================
> > +
> > +Broadcom's Starfighter 2 Ethernet switch hardware block is commonly found
> > and
> > +deployed in the following products:
> > +
> > +- xDSL gateways such as BCM63138
> > +- streaming/multimedia Set Top Box such as BCM7445
> > +- Cable Modem/residential gatewasy such as BCM7145/BCM3390
gateway
> > +
> > +The switch is typically deployed in a configuration involving between 5 to
> > 13
> > +ports, offering a range of built-in and customizable interfaces:
> > +
> > +- single integrated Gigabit PHY
> > +- quad integrated Gigabit PHY
> > +- quad external Gigabit PHY w/ MDIO multiplexer
> > +- integrated MoCA PHY
> > +- several external MII/RevMII/GMII/RGMII interfaces
> > +
> > +The switch also supports specific congestion control features which allow
> > MoCA
>
> what is MoCA? Maybe answer in "MoCA interfaces" section.
>
> > +fail-over not to loose packets during a MoCA role re-election, as well as
> > out of
>
> lose
>
> > +band back-pressure to the host CPU network interface when downstream
> > interfaces
> > +are connected at a lower speed.
> > +
> > +The switch hardware block is typically interfaces using MMIO accesses and
>
> interfaced
> or drop the "is"
>
> > +contains a bunch of sub-blocks/registers:
> > +
> > +SWITCH_CORE: common switch registers
> > +SWITCH_REG: external interfaces switch register
> > +SWITCH_MDIO: external MDIO bus controller (there is another one in
> > SWITCH_CORE,
> > +which is used for indirect PHY accesses)
> > +SWITCH_INTRL2_0/1: Level-2 interrupt controllers
> > +SWITCH_ACB: Admission control block
> > +SWITCH_FCB: Fail-over control block
> > +
> > +Implementation details
> > +======================
> > +
> > +The driver is located in drivers/net/dsa/bcm_sf2.c and is implemented as a
> > DSA
> > +driver, see Documentation/networking/dsa/dsa.txt for details on the
> > subsytem and
>
> s/,/;/
>
> > +what it provides.
> > +
> > +The SF2 switch is configured to enable a Broadcom specific 4-bytes switch
> > tag
> > +which gets inserted by the switch for every packet forwarded to the CPU
> > +interface, conversely, the CPU network interface should insert a similar
> > tag for
> > +packets entering the CPU port. The tag format is described in
> > +net/dsa/tag_brcm.c.
> > +
> > +Overall, the SF2 driver is a fairly regular DSA driver, there are a few
>
> s/,/;/ here.....................^
>
> > +specifics covered below.
> > +
> > +Device Tree probing
> > +-------------------
> > +
> > +The DSA platform device driver is probed using a specific compatible string
> > +provided in net/dsa/dsa.c. The reason for that is because the DSA
> > subsystem gets
> > +registered as a platform device driver currently. DSA will provide the
> > needed
> > +device_node pointers which are then accessible by the switch driver setup
> > +function to setup resources such as register ranges and interrupts. This
> > +currently works very well because none of the of_* functions utilized by
> > the
> > +driver require a struct device to be bound to a struct device_node, but
> > things
> > +may change in the future.
> > +
> > +MDIO indirect accesses
> > +----------------------
> > +
> > +Due to a limitation in how Broadcom switches have been designed, external
> > +Broadcom switches connected to a SF2 require the use of the DSA slave MDIO
> > bus
> > +in order to properly configure them. By default, the SF2 pseudo-PHY
> > address, and
> > +an external switch pseudo-PHY address will both be snooping for incoming
> > MDIO
> > +transactions, since they are at the same address (30), resulting in some
> > kind of
> > +"double" programming. Using DSA, and setting ds->phys_mii_mask
> > accordingly, we
> > +selectively divert reads and writes towards external Broadcom switches
> > +pseudo-PHY addresses. Newer revisions of the SF2 hardware have introduced a
> > +configurable pseudo-PHY address which circumvents the initial design
> > limitation.
> > +
> > +MoCA interfaces
> > +---------------
> > +
> > +MoCA interfaces are fairly specific and require the use of a firmware blob
> > which
> > +gets loaded onto the MoCA processor(s) for packet processing. The switch
> > +hardware contains logic which will assert/de-assert link states
> > accordingly for
> > +the MoCA interface whenever the MoCA coaxial cable gets disconnected or the
> > +firmware gets reloaded. The SF2 driver relies on such events to properly
> > set its
> > +MoCA interface carrier state and properly report this to the networking
> > stack.
> > +
> > +The MoCA interfaces are supported using the PHY library's fixed
> > PHY/emulated PHY
> > +device and the switch driver registers a fixed_link_update callback for
> > such
> > +PHYs which reflects the link state obtained from the interrupt handler.
Best,
-v
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